A patient with age-related macular degeneration undergoes fundus autofluorescence (FAF) imaging. The area of geographic atrophy appears as a well-demarcated region of hypoautofluorescence. This occurs because:
- A The RPE cells are absent, reducing the fluorophore ✓
- B There is increased lipofuscin deposition in that area
- C Drusen accumulate and block the signal
- D Subretinal fluid scatters the excitation light
Correct answer: A. The RPE cells are absent, reducing the fluorophore
Explanation
FAF signal originates from lipofuscin in RPE cells. In geographic atrophy, RPE cells are lost, so the autofluorescence signal is absent (hypoautofluorescence). Increased lipofuscin (option B) would cause hyperautofluorescence, not hypo. The absence of RPE is the direct cause of the dark, well-demarcated areas seen on FAF in geographic atrophy.
Reference: Ryan's Retina, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.